os-helpers: fs: replace wait4file w/ inotifywait

[jakogut]

Previously, scripts that required a file that is created asynchronously, such as the by-state links created by a udev rule, would busy loop until the file existed using wait4file(), part of os-helpers-fs.

This is time consuming and inefficient, as the minimum wait time adds latency to the following operations. Instead, use inotifywait to receive an event from the kernel when the relevant file or path is modified to prevent unnecessary resource usage and busy waiting.

Change-type: patch

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[alexgg]

@jakogut I think the change is an improvement, but why not keep the wait4file abstraction and just re-implement it using inotifywait?
Also, as the include option is only supported from inotify-tools 3.21.9.0, if you abstract it in wait4file you can check that a specific version is installed and if not fallback to the current method for backwards compatibility with older Yocto versions that include older versions of inotifywait (or don't have an inotify-tools recipe)

[jakogut]

Good thoughts, thanks.